The height of the compacted material and the pressure imposed thereon constitute two criteria which perform a primordial role in the behaviour of the final products when they are subseqeuntly used. Furthermore, if these criteria, at predetermined values are not respected, these products sometimes explode during manufacture, causing considerable damage to the environment in which they are manufactured.
In an attempt to determine the height of the compacted material and the pressure imposed thereon, the prior art has proposed, particularly in Patent Appln. EP-A-0 130 958, the use of a press in the form of a vertical chassis bearing, in its upper part, a jack of which the piston rod is adapted to control a punch in vertical displacement. The press is equipped, in its lower part, with a withdrawal jack designed to control displacement of a die cooperating with the punch. The control and withdrawal jacks are associated with position sensors and with force sensors.
The jacks are displaced until the values of compaction and/or of height correspond to respective reference values of force and/or of height. When the reference values of force and/or of height are attained, the values of compaction and/or height are checked to ensure that they are included between maximum and minimum values.
One drawback of the press described hereinabove resides in the fact that it does not enable the real height of compacted material and/or the real pressure imposed on the material to be precisely known. Such uncertainties as to the real height of the compacted material and the real pressure imposed on the material do not enable final products with precise and reproducible characteristics to be obtained. Moreover, such a press, by its structure, cannot take into account the mechanical tolerances and the elasticity of the various members constituting it, with the result that the measurements made are always affected by errors.
It is precisely an object of the invention to ovecome the above drawbacks, by proposing a novel compacting apparatus adapted to know the real height of compacted material and/or the real pressure imposed on the material, accurately, so as to act on the punch in order to obtain the desired height and/or pressure.
It is another object of the invention to propose a compacting apparatus offering an easy and precise capacity of adjustment of the criteria of height and of pressure, over very broad ranges of values.
A further object of the invention is to propose a press designed to receive at least one compacting apparatus according to the invention, making it possible to carry out reproducible and precise packing-compression operations in order to obtain, by transfer machine, mass-production of cartridges of pyrotechnic character with substantially identical characteristics.
Yet another object of the invention is to propose a process for measuring and correcting the elasticity of a compacting apparatus fitted on a press.